The excited states of a ${}^{78}\mathrm{Se}$ nucleus were studied via a multiple Coulomb excitation experiment. A natural lead target was irradiated by the ${}^{78}\mathrm{Se}$ beam and $\gamma$ rays in coincidence with the scattered projectiles were collected. Resulting yields were used as an input for the least squares analysis code GOSIA. Four known excited states were observed and nine matrix elements including three diagonal ones were derived from this analysis. The deformation parameter $〈Q^2〉$ was deduced by a sum rule. The results showed good agreement with the calculation by the asymmetric rotor model with triaxial deformation parameter $\gamma \simeq 23°–28°.$ The quadrupole moments of the $2_1^{+}$ and $2_2^{+}$ states analyzed by this model suggested that both levels had the same intrinsic state.

• Received 27 December 2002

DOI:https://doi.org/10.1103/PhysRevC.67.064310